The invention relates to a secondary air fan for an internal combustion engine in which a motor unit and a pump unit driven by the motor unit are arranged in a housing. The housing has an air inlet channel, an air outlet channel and an air mass sensor arranged in one of the channels for regulating the motor unit by an electronic means.
Secondary air fans of this type are known for post-oxidizing uncombusted fuel components during cold starting of the engine by forced air flow into the exhaust gases to minimize discharge of pollutants into the atmosphere. An air mass sensor supplies an actual instantaneous value of the air mass flow and the instantaneous value is supplied to an electronic unit connected, on one side, to the motor of the secondary air fan and, on another side, to an over-riding computer unit, for example, an engine control unit. The wiring cables of the air mass sensor and of the fan motor to the electronic unit have a disadvantage in the known construction, since the cables cause an increased expenditure for assembly and also the cables are very sensitive to disruption. Furthermore, the electronic unit requires room for assembly.
An object of the invention is to provide a secondary air fan, which avoids the above disadvantages.
This object is achieved according to the invention by arranging the air mass sensor, at the electronic unit and attaching the electronic unit to the housing and/or to the air inlet or air outlet channel.
In this way, the wiring of the air mass sensor to the electronic unit is not necessary. In addition, by introducing the electronic unit in the region of one of the air channels, a cooling of the electronic unit is automatically obtained.
It is particularly advantageous if the parts of the electronic unit to be cooled, are located behind the air mass sensor, in the direction of air flow, so that the air mass flow is not influenced by heat exchange.
Furthermore, due to the construction of the invention, the electronic unit does not require any additional room for its assembly.